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Center for Nonlinear Studies |
We explore the role of non-adiabatic effects on acetaldehyde (CH3CHO) photodissociation mechanisms using ab initio non-adiabatic molecular dynamics simulations. The photodissociation is simulated using linear-response time-dependent density functional theory by propagating the trajectories on the S1 and S0 potential energy surfaces and the non-adiabatic effects are taken into account using Tully's surface hopping algorithm. To describe mechanisms involving open-shell intermediates and products, i.e., homolytic dissociation of sigma-bonds, we developed and employ a novel spin-symmetry breaking algorithm. Comparisons between ensembles initiated in the ground and excited states shows that the non-adiabatic effects play only a minor role in reproducing the experimental branching ratios but may have significant contribution on the atomistic level mechanisms. Additionally, a new concerted triple-fragmentation mechanism is identified and non-adiabatic effects on the "roaming" mechanism for methane production are discussed.
Host: Tammie Nelson